John Cattanach pitched in three games in the major leagues, all in 1884. He went 1-1, with an ERA+ of 84 in 22 innings. Interestingly, Cattanach pitched for two pennant winners that year, the Providence Grays of the NL and the St. Louis Maroons of the UA.
A tall, strong, and graceful athlete who was raised on Providence's East Side, and a champion rower with the Narragansett Boat Club, Cattanach had been training all spring under [Fred] Bancroft's tutelage to made the difficult leap to professional baseball. With his muscular arms and thick upper torso, he could throw the ball impressively hard, but like many novices he had serious trouble finding the plate, and Bancroft did not entirely trust him at the major-league level...[On June 5, Bancroft] had little choice but to send to the box his not-yet-ripe spring project, the champion rower John Cattanach-risky business, because the twenty-one year-old was still suffering control problems. Sure enough, before a slender crowd of four hundred at Messer, the tall, barrel-chested rookie proved nervous and wild, surrendering seven runs to the Phillies in little more than four innings. Sweeney, whom Bancroft had prudently stowed in right field, traded places with the flustered rower. But even banished to the outfield, Cattanach proved a detriment, contributing a costly error to the Grays' 9-8 defeat. "Cattanach needs practice, but it ought to be with a semi-professional nine," the Evening Press jabbed.-Fifty-Nine in '84
Ed Achorn went on to write that after Radbourn had proved, once again, that his tired arm could withstand the strain of a heavy workload, Bancroft released Cattanach on June 16. I found a notice of his release in the Cleveland Herald on June 20 but can't seem to find any record of the Maroons signing him. One has to assume that he was signed sometime around the same time as the Maroons were signing Boyle and Ryder. Regardless, Cattanach was the first former Gray to pitch for the Maroons in 1884 but he would not be the last.